Urban Wastewater Treatment in Turkey

The Ninth National Development Plan established for the period 2007-2013 [11]. On the other hand states that, according to the statistical information gathered from 1,911 municipalities out of the total number of 3,225, 80% of the population benefits from sewer systems, 47% are provided with wastewater treatment, whereas 93% of the total population is supplied with drinking water, but only 42% is being served by drinking water treatment facilities. The development plan also stipulates that European Union (EU) legislations will be adopted and applied, reliable and integrated information systems will be established and tracking, auditing and reporting infrastructure will be further developed.

Based on a nationwide data inventory accomplished in the years 2003 and 2006 within the scope of an EU-funded MEDA-Water project [12], in Turkey there are currently around 131 urban wastewater treatment plants in operation, out of which 41 are located in settlements with less than 10,000 inhabitants and 28 in settlements with more than 100,000 inhabitants ([13] and 2006). Among the 131 treatment plants, 51 apply preliminary (physical) treatment, 73 operate secondary (biological) treatment units, and the remaining 7 treatment plants practice tertiary treatment for advanced nitrogen and phosphorus removal. Actually, only 55% of the total Turkish population is served by the state-owned sewage treatment works [13].

Table 31.1 Discharge limits values foreseen in the National Urban Wastewater Treatment Directive [14]


Maximum concentration (mg/L)

Minimum required treatment efficiency (%)

BOD5 (nitrification excluded)15 COD TSS


90c 90a

aAt locations that are 1,500 m or higher above the sea level and where temperatures are often too low for efficient biotreatment, urban wastewater discharge can be carried out at higher effluent parameter values bIn case that a correlation can be established between a parameter that can be used instead of the BOD5 parameter such as total organic carbon, TOC, or total oxygen demand, TOD, a parameter replacement is possible cThis condition is population-dependent

In order to meet the requirements of the Urban Wastewater Treatment Directive 91/271/EEC, the national wastewater directive for the discharge of urban wastewater to the municipal sewage system has been recently published as an amended by-law on urban wastewater treatment in 2006 [14, 15] (Table 31.1).

This legislation covers the discharge of urban wastewater into receiving water bodies as well as the design, construction and collection of municipal sewage, with special emphasis on treatment principles that have to be applied according to the population equivalencies and sensitivity of the receiving water body [14]. Additionally, time frames have been allocated to construct and operate wastewater treatment plants and sewer collectors, as well as to meet the requirements of the amended by-law on population equivalencies (P.E.) changing between less than 2,000 to more than 100,000 P.E [15].

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